Employee Benefit Plans - Postretirement Healthcare Plan (Details) - Postretirement Healthcare Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure
Minimum age requirement	55 years
Requisite service period	15 years
Unfunded benefit obligation	$ 667	$ 3,921
Net periodic benefit cost	$ 209	$ 400	$ 400
Assumptions used calculating net periodic benefit cost, discount rate	2.40%	3.60%
Assumptions used calculating net periodic benefit cost, rate of compensation increase	6.00%	6.00%
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2015	$ 154
2016	131
2017	125
2018	98
2019	69
2020 through 2024	121
Accumulated other comprehensive income (loss), before tax, related to the Plan	2,794	$ 267
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	2,794
Accumulated other comprehensive income (loss), net of tax	2,038
Net acturarial loss, net of tax	31
Unamortized transition asset, net of tax	37
Defined Benefit Plan, Plan Amendments	2,044
Estimated amount amortized from accumulated other comprehensive loss into net periodic benefit costs	$ 562